With continuous development of technology, electronic and digital products are renewed more and more frequently and various new products are manufactured at the same time. E-paper is also called digital paper. As a resultant of a combination of information display characteristics of ordinary paper and characteristics of a computer display screen, the E-paper is a new product emerging in the digital product market in recent years. Since the E-paper can reproduce the display characteristics of the ordinary paper and is reusable, consumption in the ordinary paper may be reduced, and no great damage is caused to environment. In addition, the E-paper has many advantages such as motion picture display. Therefore, the E-paper will replace ordinary paper documents as a display means.
FIG. 1 is a schematic structural view of an E-paper. Active E-paper is mainly formed by an upper substrate 1, an E-ink layer 2, and a lower substrate 3. The E-paper display is a reflective display which needs no background light source and displays data by reflecting an environment light source. The E-ink layer 2 contains white pigment particles 21 and black pigment particles 22, in which the white pigment particles 21 having a good reflecting ability are used to display a bright state, while the black pigment particles 22 having a good absorbing ability are used to display a dark state. Since the E-paper needs no background light source, a thin film transistor (TFT) array substrate driving the E-paper and a substrate driving a liquid crystal display (LCD) are of different structures. The manufacturing process of an array substrate driving the E-paper has gradually become mature in recent years, but is mainly based on a 5mask or 4mask process, with complex process and high cost. Someone has proposed to directly use a drain electrode as a driving electrode to simplify the above process, and fabricate the array substrate driving the E-paper only with a 2mask. FIG. 2 is a schematic structural view of an E-paper array substrate in the prior art. As shown in FIG. 2, the array substrate fabricated by the 2mask process is formed by a glass substrate (Glass) 4, a gate electrode (Gate) 5, a storage capacitor bottom electrode (Cs bottom electrode) 6, an insulator layer (Insulator) 7, an amorphous silicon (a-Si) layer 8, an n+ a-Si layer 9, a source/drain (S/D) metal layer 10, and a passivation film (PVX) 11. However, such a method causes steps in the structure of the array substrate, for example, unevenness in the surface of the passivation film 11 in FIG. 2, which causes difficulties in the coating of E-ink during the subsequent process and non-uniform distribution of a drain electric field, thus affecting the display effect of the E-paper.